Georgia Bulldogs quarterback Aaron Murray (11) throws during last Thursday’s practice at the University of Georgia. (Dale Zanine-USA TODAY Sports)

Last year, Georgia’s defense was supposed to be a known quantity.

After a much improved 2011 campaign, the summer of 2012 was spent talking about potential All-Americans Jarvis Jones, Alec Ogletree and Bacarri Rambo. The bulk of Todd Grantham’s defensive unit was returning — save for cornerback Brandon Boykin and defensive end Deangelo Tyson — and the Bulldogs were poised for greatness. By many measures, the end result was disappointing.

This year, the known quantity is the offense as Mike Bobo returns a plethora of weapons.

With a young defense and a brutal schedule, simply maintaining will not be enough for this high-powered offensive unit. Where the defense took a few steps back in 2012, the offense needs to stride forward in 2013.

That’s no easy task for an offense that is coming off of school records for points, yards and first downs in a single season. It’s never easy for the best to get better, but it’s possible.

Any improvement for this offense will start with the offensive line play. Georgia returns all five starters along the offensive line, and that cohesive unit from a year ago will be backed up by an equally seasoned group of reserves who hope to give Aaron Murray time in the pocket and the running backs holes. Furthermore, younger players like John Theus (14 starts as a true freshman) and even Wesleyan grad David Andrews (who was just a true sophomore last year when he started 14 games at center) will continue to develop.

Murray will be without his leading receiver from 2012, Tavarres King, and Marlon Brown, who came on strong before injury. But their departures will be countered by the return of Michael Bennett (the team’s leading receiver before going down with an injury after Week 5) and the rise of Malcolm Mitchell. After posting 572 yards and four touchdowns while sharing time with duties as a defensive back, Mitchell will be exclusive to Bobo’s offense in 2013. Combine those two receivers’ increasing work loads with a host of young playmakers (guys like Chris Conley and Justin Scott-Wesley) hoping to break out of the shadows, and there won’t be a drop off in sure-handed pass catchers.

Tight end Arthur Lynch is showing up on most pre-season All-SEC lists after a 431-yard season in 2012, and some still argue that he is not the best tight end on the team. Jay Rome had fewer opportunities but still managed to average nearly 14 yards per catch in 2012 while hauling in two touchdown passes (including a huge one against Alabama in the SEC Championship Game).

Todd Gurley and Keith Marshall proved to be spark plugs for the Georgia offense last year as the duo accounted for over 2,300 yards of offense and 27 total touchdowns. They will be relied upon more heavily moving forward as running the ball and eating up the clock will give a young defense time to rest. But, the possibility of seeing both heads of the monster that is “Gurshall” in the backfield at the same time (a look that Bobo experimented with during the Capital One Bowl) could add another element to an already electric offense.

Ultimately, the offense will ride the shoulders of Murray for a fourth consecutive year. The quarterback didn’t spurn NFL riches (at least for a little while) for a chance to merely come back. He put off his childhood dream for a chance to improve — both individually and as a team

If Murray is a shadow of what he was last year he will threaten almost every SEC career passing record. But, if there is a spot where Murray can improve, look at accuracy.

Last year Murray completed 64.5 percent of his passes (an increase of nearly 5.5 percent from 2011). If he can knock on the door of 70 percent this year, then the offense will likely surpass the performance of 2012.